French philosopher, converted to Catholicism and ordained a priest in 1816. In his early writings, Lamennais combat on the one hand the "freedoms" advocated by the revolution, and on the other hand, defend the authority of the Pope over bishops and churches, against the galicanas trends. To this period belong the works: reflections on the State of the Church in France during the 18th century (1808), tradition of the Church on the institution of Bishops (1814) and essay on indifference in religious matters (1817-23, book that placed him in the forefront of the cultural and social life of the time). However, years later abandons his counter-revolutionary attitude, claiming the "modern freedoms" and defends the reconciliation between Catholicism and liberalism in his work on the progress of the revolution and the struggle against the Church (1829) and, above all, in the newspaper L'Avenir, which he founded along with Lacordaire and others in 1830. He called for the separation of Church and State, opposed the Royal appointment of bishops and the clergy proposed real independence from political power. Pope Gregorio XVI condemned the position of the French Liberal Catholic. In the words of a believer, Lamennais was reaffirmed in his theories, longing for a Christianity stripped of designed fully in the social field, democratic and spiritual dimension. Thereafter he devoted himself to politics, militant in the Democratic Party.